The backlash against Facebook's "free mobile data" Internet.org scheme has spread across the globe.

A total of 67 digital rights groups - including i Freedom Uganda, Ecuador's Usuarios Digitales and Indonesia's ICT Watch - have signed a letter to Facebook's founder, Mark Zuckerberg, stating concerns about the initiative.

They say the project threatens freedom of expression, privacy and the principle of net neutrality.

Facebook continues to defend its offer.

"We are convinced that as more and more people gain access to the internet, they will see the benefits and want to use even more services," a spokesman told the BBC.

"We believe this so strongly that we have worked with operators to offer basic services to people at no charge, convinced that new users will quickly want to move beyond basic services and pay for more diverse, valuable services."

What is Internet.org?

http://www.bbc.co.uk/news/technology-32795270